This invention relates generally to rechargeable batteries and more particularly to a rechargeable battery for hand-held radio equipment which may be recharged from either a direct current (DC) power source or a high voltage alternating current (AC) power source such as the commonly available 120VAC mains. Integral means are provided to protect against electrical hazards.
Portable electronic equipment is conventionally powered by batteries. The batteries often are of the type which can be recharged by application of a suitable DC charging power over a period of time. The easiest method of such recharging is to remove the batteries from the electronic equipment, place them into a separate charging apparatus, plug the charging apparatus into a standard wall socket, and allow the charging apparatus to charge the batteries. This charging is typically accomplished by reducing the 120VAC available at the receptacle to a lower voltage, rectifying it, and controlling the current applied to the batteries. It has become commonplace for products such as flashlights to employ removable and rechargeable batteries.
In some portable flashlights, the batteries are removable as a single package which further contains rectifying and voltage reducing circuitry as well as the dual pronged plug for plugging the battery package into the standard receptacle 120VAC mains. In other flashlights, the batteries, rectifying and voltage reducing circuitry, and plug are contained in one housing. Such a rechargeable flashlight is shown in FIG. 1 and represents a product generally available as the Flashliter.sup..TM. from Black & Decker (U.S.), Inc., Shelton CT. As illustrated in FIG. 1, the plug 101 for this flashlight pivots about a point near one end of the plug prongs (201 in FIGS. 2A and 2B) so that the plug may be rotated such that the prongs 201 are positioned at or below the surface of the housing 203 of the flashlight when not in use (as shown in FIG. 2A) or extended above the surface (as shown in FIG. 2B) when the plug is to be used. The prongs 201 are rotated by a switch mechanism 205 when placed in the third of three operating positions: the "charge" position. The pivoting of the prongs 201 of the plug 101 brings the interior portions of the prongs 201 into contact with contacts 207 which are used to connect the prongs to the rectifying circuitry when the prongs are extended from the housing. When the prongs 201 are rotated into the housing, the connection to the contacts 207 is removed. The remaining two switch mechanism 205 positions, "on" and "off", place contact springs 209 (which are not related to the plug 101) in a position to complete the battery circuit to the flashlight light bulb or to disconnect the battery-light bulb circuit, respectively. In this integral flashlight, the electrical connection between the batteries and the lightbulb is inaccessible to the user and therefore does not present a hazard to the user when the batteries are being recharged.
Rechargeable batteries for portable radios, particularly two-way radio transceivers, are powerful energy storage elements which are typically enclosed in a housing having electrical contacts capable of conducting significant amounts of current for charging the batteries and for conducting electricity from the batteries to the transceiver. For convenience, the battery package may be left attached to the portable transceiver for charging or the battery may be disconnected for charging. In either instance, the portable battery is recharged from a conventional external DC charging apparatus. To be truly portable, however, a portable radio and its battery should be independent of any external charging apparatus. Thus, it is highly desirable that the battery for a portable radio be capable of being recharged without being dependent upon an external device and its associated wires and connections while maintaining a capability of being so recharged. If such a battery were rechargeable from the commonly available 120VAC power, the battery necessarily must not present a hazard to the individual attempting to recharge the battery. Thus, protection must be provided against a 120VAC shock hazard and from accidental contact with the standard DC charging contacts (which can present high discharge currents and subject the batteries to serious damage if shorted).